The 45S rRNA precursor gene sequence (Small Subunit ribosomal RNA (SSU rRNA) gene-Internal Transcribed Spacer-1 (ITS-1)˜5.8S ribosomal RNA (5.8S rRNA) gene˜Internal Transcribed Spacer-2 (ITS-2)˜Large Subunit ribosomal RNA (LSU rRNA) gene) has been used for the classification of species. For example, according to the method developed by Shin J H, et al. (J. Clin. Microbiol., 37: 165-170 (1999)), 5 candida species (fungi) of the genus Candida can be detected and identified using two primers hybridized to the 5.8S rRNA and 28S rRNA (LSU rRNA) gene sequences common to fungi and 5 separate probes each of which can specifically hybridize to the ITS-2 sequence of its corresponding species. The method is different from the present invention as described below. Firstly, the method is aimed at fungi, specifically candida (fungi). Secondly, the method does not use the primers, which hybridize to ITS-1 or ITS-2 sequence. Consequently, these primer pairs do not assure the specificity to the genus Candida, whereas each of five probes can independently recognize its corresponding candida species (fungi) of the genus Candida. In other words, only one species of the genus Candida can be detected and identified when a single set of the primer pair and a probe is used. Thirdly, the above publication does not describe about the sensitivity of the detection, which is very important for the detection methods of allergenic plants in food. Lastly, the method needs expensive reagents and instruments due to the use of probes.
According to the method developed by Proft J, et al. (Parasitol. Res., 85: 837-843 (1999)), a certain anopheles mosquito can be classified into one of 6 species of the genus Anopheles using 6 primer pairs. The method uses a primer that can hybridize to the 5.8 rRNA gene sequence common to the six anopheles mosquito species of the genus Anopheles in combination with 6 primer pairs each of which can specifically hybridize to the ITS-2 sequence of its corresponding anopheles mosquito species of the genus Anopheles. Based on the size of the amplification product obtained by PCR method, the anopheles mosquito of interest can be classified into one of the 6 species of the genus Anopheles. The method is different from the present invention as described below. Firstly, the method is aimed at mosquitoes, specifically the anopheles mosquitoes. Secondly, due to the properties of designed primer pairs, only one species of the genus Anopheles can be detectable when a single primer pair is used. Thirdly, an object of the method is to identify a specimen exclusively derived from a single species of mosquitoes. Consequently, the object of the method is not to analyze anopheles mosquitoes in a mixture. Lastly, the above publication does not describe about the sensitivity of the detection, which is very important for the detection methods of allergenic plants in food.
Thus, the conventional methods mentioned above are to detect one specific species in a mixture and to identify a bio specimen exclusively derived from a single species of the genus, and therefore, the methods do not relate to a method for detecting the target genus broadly in cases where even one kind of the target genus is contained in a mixture. In addition, the primer sequences common to several species are located on SSU rRNA, 5.8S rRNA and LSU rRNA gene sequence, and therefore, primer sequences common to several species are not found in ITS-1 or ITS-2 sequence.
On the other hand, regarding detection of allergenic plants in food, a method for detecting whether some wheat is contained in a food sample of interest is disclosed by Allmann M, et al. (Z Lebensm Unters Forsch, 196: 248-251 (1993)). The method uses primers which specifically hybridize to a IGS sequence between 25S rRNA (LSU rRNA) and 18S rRNA (SSU rRNA) gene sequences of wheat. However, it is hard to evaluate the specificity of the primers by simulation and the like because the primers have to be designed based on little information about the IGS sequence in the method. Therefore, it would be difficult to judge the reliability of the analysis.